A basic structure of a conventional stator coil is a unitary structure that includes a linear part of the coil that forms a straight line in an axial direction (longitudinal direction) parallel to a rotation axis center, a coil end (curved part), and a field alleviating layer. The coil end is wound around a stator core and protrudes from an axial end face, forming an involute shape. The stator core is formed of a layered body of metal plates, for example, with a slot radially formed (a groove extending in a radial direction) on a plurality of portions in a circumferential direction of an inner periphery. The coil end is electrically integral with the linear part of the coil via the field alleviating layer.
In a turbine generator or a water-wheel generator as a rotating electrical machine, a coil end has an involute curve, as described above, and the shape of the coil end differs for each product number of the electric generator. Therefore, it is necessary to produce a coil end having a complicated shape for each product number.
Also, in storing a coil in a slot, the shape of the coil end is complicated, as described above, and therefore it is necessary to perform the operation of picking up several coils, the so-called pick-up coil, when storing, in a slot, the final coil to be stored in the slot, which presents a challenge to the operation process.